US5162661A - Position detector for maintaining a fixed distance between two objects - Google Patents

Position detector for maintaining a fixed distance between two objects Download PDF

Info

Publication number
US5162661A
US5162661A US07/608,926 US60892690A US5162661A US 5162661 A US5162661 A US 5162661A US 60892690 A US60892690 A US 60892690A US 5162661 A US5162661 A US 5162661A
Authority
US
United States
Prior art keywords
light receiving
distance
receiving means
light
detectors
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
US07/608,926
Other languages
English (en)
Inventor
Katsuharu Sato
Shoji Taniguchi
Naoharu Yanagawa
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Pioneer Corp
Original Assignee
Pioneer Electronic Corp
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority claimed from JP2027189A external-priority patent/JPH0782653B2/ja
Priority claimed from JP2027190A external-priority patent/JPH0782654B2/ja
Application filed by Pioneer Electronic Corp filed Critical Pioneer Electronic Corp
Assigned to PIONEER ELECTRONIC CORPORATION reassignment PIONEER ELECTRONIC CORPORATION ASSIGNMENT OF ASSIGNORS INTEREST. Assignors: SATO, KATSUHARU, TANIGUCHI, SHOJI, YANAGAWA, NAOHARU
Application granted granted Critical
Publication of US5162661A publication Critical patent/US5162661A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

Links

Images

Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
    • G01B11/00—Measuring arrangements characterised by the use of optical techniques
    • G01B11/02—Measuring arrangements characterised by the use of optical techniques for measuring length, width or thickness
    • G01B11/026—Measuring arrangements characterised by the use of optical techniques for measuring length, width or thickness by measuring distance between sensor and object
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01D—MEASURING NOT SPECIALLY ADAPTED FOR A SPECIFIC VARIABLE; ARRANGEMENTS FOR MEASURING TWO OR MORE VARIABLES NOT COVERED IN A SINGLE OTHER SUBCLASS; TARIFF METERING APPARATUS; MEASURING OR TESTING NOT OTHERWISE PROVIDED FOR
    • G01D5/00—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable
    • G01D5/26—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light
    • G01D5/28—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with deflection of beams of light, e.g. for direct optical indication
    • G01D5/30—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with deflection of beams of light, e.g. for direct optical indication the beams of light being detected by photocells
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B11/00—Recording on or reproducing from the same record carrier wherein for these two operations the methods are covered by different main groups of groups G11B3/00 - G11B7/00 or by different subgroups of group G11B9/00; Record carriers therefor
    • G11B11/10—Recording on or reproducing from the same record carrier wherein for these two operations the methods are covered by different main groups of groups G11B3/00 - G11B7/00 or by different subgroups of group G11B9/00; Record carriers therefor using recording by magnetic means or other means for magnetisation or demagnetisation of a record carrier, e.g. light induced spin magnetisation; Demagnetisation by thermal or stress means in the presence or not of an orienting magnetic field
    • G11B11/105—Recording on or reproducing from the same record carrier wherein for these two operations the methods are covered by different main groups of groups G11B3/00 - G11B7/00 or by different subgroups of group G11B9/00; Record carriers therefor using recording by magnetic means or other means for magnetisation or demagnetisation of a record carrier, e.g. light induced spin magnetisation; Demagnetisation by thermal or stress means in the presence or not of an orienting magnetic field using a beam of light or a magnetic field for recording by change of magnetisation and a beam of light for reproducing, i.e. magneto-optical, e.g. light-induced thermomagnetic recording, spin magnetisation recording, Kerr or Faraday effect reproducing
    • G11B11/1055—Disposition or mounting of transducers relative to record carriers
    • G11B11/10576—Disposition or mounting of transducers relative to record carriers with provision for moving the transducers for maintaining alignment or spacing relative to the carrier
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
    • G11B7/08—Disposition or mounting of heads or light sources relatively to record carriers
    • G11B7/09—Disposition or mounting of heads or light sources relatively to record carriers with provision for moving the light beam or focus plane for the purpose of maintaining alignment of the light beam relative to the record carrier during transducing operation, e.g. to compensate for surface irregularities of the latter or for track following
    • G11B7/095—Disposition or mounting of heads or light sources relatively to record carriers with provision for moving the light beam or focus plane for the purpose of maintaining alignment of the light beam relative to the record carrier during transducing operation, e.g. to compensate for surface irregularities of the latter or for track following specially adapted for discs, e.g. for compensation of eccentricity or wobble
    • G11B7/0956—Disposition or mounting of heads or light sources relatively to record carriers with provision for moving the light beam or focus plane for the purpose of maintaining alignment of the light beam relative to the record carrier during transducing operation, e.g. to compensate for surface irregularities of the latter or for track following specially adapted for discs, e.g. for compensation of eccentricity or wobble to compensate for tilt, skew, warp or inclination of the disc, i.e. maintain the optical axis at right angles to the disc
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
    • G01B2210/00—Aspects not specifically covered by any group under G01B, e.g. of wheel alignment, caliper-like sensors
    • G01B2210/40—Caliper-like sensors
    • G01B2210/44—Caliper-like sensors with detectors on both sides of the object to be measured

Definitions

  • the present invention relates to a device for maintaininq a fixed distance between two objects, for example, a distance between a magnetic head and a disk. More particularly, the invention relates to a device for maintaining a fixed inclination between the two objects as well as the distance therebetween.
  • FIG. 1 One device for maintaining a fixed distance between a measuring device and an object to be measured, is as shown in FIG. 1.
  • reference character "a” designates a laser light source, such as an He - Ne laser; "b”, a paired light receiving means; and "c", the surface of an object under measurement.
  • the light source "a” must be slanted with respect to the surface "c" of the object under measurement, in order that the reflected light is directed to the light receiving means "b".
  • an angle ⁇ of the light emitted from the light source should be preferably increased.
  • a distance between the light source “a” and the light receiving means “b” must be increased.
  • the light receiving means “b” consists of two elements b 1 and b 2 , and hence tends to be bulky. Due to the above two factors, the position detector necessarily becomes bulky. The inclination of the surface "c" frequently causes a great measurement error.
  • FIG. 2 A known device to correct the inclination of the surface to be measured is as shown in FIG. 2.
  • Light receiving elements b 3 and b 4 have the same size, and are disposed equidistant from a light source "a".
  • the surface is moved so as to zero a difference between the output signals of the elements b 3 and b 4 .
  • this device is unable to measure the distance between the light receiving elements and the surface to be measured.
  • neither of the conventional devices is able simultaneously to correct the distance between the light receiving elements and the surface to be measured, and the inclination of the surface.
  • an object of the present invention is to provide a position detector which is small in size and which is little influenced by an inclination of an object under measurement.
  • Another object of the present invention is to provide a position detector which is small in size, and is able to maintain a fixed distance between a light receiving means and the surface of an object under measurement, and also to correct an inclination of the surface.
  • a position detector comprising light emitting means for irradiating the surface of an object to be measured, and two light receiving means for receiving light reflected by the measured surface, a distance from one of the light receiving means to the measured surface as viewed in the vertical direction being different from a distance from the other to the measured surface, wherein a correction quantity for correcting the distances between the light receiving means and the measured surface is calculated on the basis of a difference between the output signals of the light receiving means, and the distances between the measured surface and the light receiving means is corrected in accordance with the correction quantity, whereby the difference between the light receiving means and the measured surface, is kept constant, following movement of the measured surface.
  • a position detector comprising light emitting means, and two light receiving means for receiving light as emitted from the light emitting means and reflected by the measured surface, a distance from one of the light receiving means to the light emitting means being different from a distance from the other to the light emitting means, wherein a correction quantity for correcting the distances between the light receiving means and the measured surface is calculated on the basis of a difference between the output signals of the light receiving means, and the distance correction quantity is applied to moving means, thereby to correct the distances between the measured surface and the light receiving means.
  • a position detector comprising at least one light emitting means for irradiating the surface of an object to be measured, and two light receiving means symmetrically disposed with respect to the light emitting means, a distance from one of the light receiving means to the light emitting means being different from a distance from the other to the light emitting means, wherein a correction quantity for correcting the distances between the light receiving means and the measured surface is calculated by comparing the output signals of the light receiving means, and an angle of the measured surface is calculated by comparing the output signals of the light receiving means being symmetrically disposed with respect to the light emitting means, whereby the distances between the light receiving means and the measured surface and the angle of the measured surface are both corrected.
  • FIG. 1 is an explanatory diagram showing an arrangement of a conventional position detector which is able to correct a distance from a light receiving means to the surface of an object to be measured;
  • FIG. 2 is an explanatory diagram showing an arrangement of another conventional position detector which is able to correct an inclination of a measured surface
  • FIG. 3 is a diagram showing, in schematic and block form, a first embodiment of the present invention in which a position detector of the invention is incorporated into an optomagnetic recording/reproducing apparatus;
  • FIG. 4(a) is a diagram showing a key portion of the recording/reproducing apparatus of FIG. 3;
  • FIG. 4(b) is a plan view showing light receiving means used in the apparatus of FIG. 3;
  • FIG. 5 is a graph showing a relationship between an output power signal P of each light receiving means is in relation to a distance H from the light receiving means to the surface of an object to be measured;
  • FIG. 6 is a circuit diagram showing a calculating means used in the recording/reproducing apparatus of FIG. 3;
  • FIGS. 7(a) through 9(b) are diagrams useful in explaining a position detection when a measured surface is slanted
  • FIG. 10 is a diagram showing a second embodiment of a position detector according to the present invention.
  • FIG. 11 is a diagram showing a third embodiment of a position detector according to the present invention, in which a single light emitting means is shared by a pair of light receiving means;
  • FIG. 12 is a diagram showing, in schematic and block form, a fourth embodiment of the present invention in which a position detector of the invention is incorporated into an optomagnetic recording/reproducing apparatus;
  • FIG. 13 is a cross-sectional diagram taken along line I--I in FIG. 12;
  • FIG. 14 is a graph showing a relationship between an output power signal P of each light receiving means with respect to a distance H from the light receiving means to the surface of an object to be measured;
  • FIG. 15 is a diagram showing a fifth embodiment of a position detector according to the present invention, in which the light receiving means is triangular in shape;
  • FIG. 16 is a diagram showing a sixth embodiment of a position detector according to the present invention, in which the light receiving means is trapezoidal in shape;
  • FIG. 17 is a graph showing a relationship between an output power signal P of each light receiving means with respect to a distance H from the light receiving means to the surface of an object to be measured in the embodiment of FIG. 16;
  • FIG. 18 is a diagram showing a seventh embodiment of a position detector according to the present invention, which is able to correct both the distance from the light receiving means to the measured surface and the angle of the measured surface.
  • a position detector according to the present invention is incorporated into an optomagnetic recording/reproducing apparatus.
  • the position detector is used for maintaining a fixed distance between a magnetic head and a disk.
  • reference numeral 1 designates a magnetic head section for developing an external magnetic field
  • 2 an optical head section for emitting a laser beam and detecting a reflected laser beam
  • 3 a servo control section for effecting a focus servo in the optical head section 2
  • 4 a disk having a surface to be measured
  • 5 and 5' photo detectors and 6 a calculating means for calculating a correction amount from a difference between the output signals of the two photo detectors 5 and 5'.
  • a magnetic head 11 together with a magnetic actuator coil 12 functioning as a moving means, is fixed to a plate spring 13. Both ends of the plate spring 13 are held by the block 14. As a result, the magnetic head 11 is biased to a neutral point.
  • a yoke 15 and a magnet 16 are fixed to the block 14.
  • the moving means 12 is disposed in a magnetic circuit formed of the yoke 15 and the magnet 16.
  • Support tables 11' and 11" which are continuously extended from a single member, are disposed on both sides of the magnetic head 11.
  • Photo detectors 5 and 5' which are physically and electrically equal to each other, are provided on the support tables 11' and 11", respectively.
  • the photo detector 5 includes a light emitting means 5a and a light receiving means 5b.
  • the photo detector 5, likewise includes a light emitting means 5a' and a light receiving means 5b. As best illustrated in FIG. 4(a), the photo detectors 5 and 5' confront a surface of the disk 4.
  • the detector 5 is separated from the disk by a distance H as viewed in the vertical direction (i.e., as viewed in a direction substantially perpendicular to the normal surface posture of the disk), and the detector 5' is separated from the disk by the sum of the distance H and another distance L.
  • a light beam emitted from the light emitting means 5a is reflected by the surface of the disk 4, and reaches a plane including the light receiving means 5b and irradiates a circular area 5c shown in FIG. 4(b).
  • a light beam emitted from the light emitting means 5a' likewise is reflected by the surface of the disk 4, and reaches a plane including the light receiving means 5b' and irradiates a circular area 5c' shown in FIG.
  • Each of the light receiving means 5b and 5b' produces an output signal which depends on an intensity of the reflected light, and applies it to the calculating means 6. Then, the calculating means 6 supplies a drive current to the moving means 12.
  • the drive current becomes zero when the distance between the magnetic head 11 and a vertical magnetic film 4a of the disk 4 is appropriate (i.e., is of a predetermined distance).
  • the polarity and level of the drive current changes or varies in accordance with a displacement of the head in the vertical direction. This will subsequently be described in detail.
  • the magnetic head 11 When no drive current is supplied to the moving means 12, the magnetic head 11 is at the neutral position. When the drive current is fed to the moving means 12, the magnetic head 11 moves to a preset position (in the direction of arrow A in FIG. 3) in accordance with the direction and the magnitude of the drive current.
  • the photo detectors 5 and 5', together with the magnetic head 11, are moved, because such components are coupled with one another by the support tables 11' and 11".
  • the distance from the disk 4 to the photo detectors 5 and 5' as viewed in the vertical direction, and the distance between the photo detectors and the magnetic head 11 as viewed also in the vertical direction are preset, so that the drive current fed from the calculating means 6 becomes zero at an optimum distance between the magnetic head 11 and the vertical magnetic film 4a.
  • a laser beam emitted from a semiconductor laser 21 is transmitted through a beam splitter 22, and is condensed toward the disk 4 by means of an objective lens 23.
  • a laser beam reflected by the vertical magnetic film 4a of the disk 4 is transmitted through a disk substrate 4b and condensed by the objective lens 23, and then is directed toward a focus error detecting portion 24 by means of the beam splitter 22.
  • the focus error detecting portion 24 generates a focus error signal by, for example, an astigmatism method, and outputs it to the servo control section 3.
  • the objective lens 23 is fixed to an objective actuator coil 25.
  • the objective lens 23 is moved in the direction of arrow B in FIG. 3, in accordance with the direction and magnitude of a drive current fed to the actuator coil 25.
  • a focus servo unit 31 generates a servo signal by using a focus error signal as input thereto, and outputs it to a focus driver unit 32.
  • the unit 32 generates a drive current for focus servo, which varies in accordance with the servo signal, and feeds it to the actuator coil 25.
  • the actuator coil 25 moves the objective lens 23 in a direction to correct a focus error in accordance with the drive current as fed thereto. In this way, the servo control is performed so as to maintain a fixed distance between the disk 4 and the objective lens 23.
  • the light emitting means 5a of the photo detector 5 irradiates the measured surface or disk 4 within the circular area 5c whose radius depends on the distance from the disk 4.
  • the photo detector 5' Part of the reflected light beam from the disk 4 is incident on, and detected by, the light receiving means 5b and 5b', which in turn produce output signals reflecting the amounts of the received light.
  • the instant embodiment does not use FIG. 1's paired light receiving means which each receive reflected light when a disk is at a different posture or distance. Because of this, the angles of the light beams emitted from the light emitting means 5a and 5a' may be small. The distance between each light emitting means 5a and 5a' and each light receiving means 5b and 5b' may also be small. As a result, the size of the photo detectors may be reduced.
  • a graphical representation of a relationship between an output power P of each light receiving means 5b and 5b' and the distance H from the disk 4 to each photo detector is as shown in FIG. 5.
  • the ordinate represents the output power P of the light receiving means
  • the abscissa represents the distance H.
  • the reason for this is that when the photo detector is too close to the measured surface, the reflected light is hardly incident on the light receiving means. Accordingly, the curve (1) starts from an origin 0, peaks an Ho, and then gradually falls off.
  • a curve (2) indicates a variation of the output power P of the light receiving means 5b' which is more distant from the measured surface.
  • a profile of the curve (2) resembles that of the curve (1), but as a whole is shifted to the left by the distance L, since the distance of the light receiving means 5b' from the measured surface is H+L.
  • a difference between the curves (1) and (2) provides a curve (3). If a value of L is too small, both the curves (1) and (2) approach each other. Under such condition, a difference between curves (1) and (2) can hardly be detected. To avoid this, distances of the detectors are set to a condition when preferably L>Ho. By using the value of a curve (3) thus obtained for a servo signal, the magnetic head 11 is moved, thereby to maintain a fixed distance between the magnetic head 11 and the measured surface 4.
  • a position of the magnetic head 11 relative to the photo detectors 5 and 5' is selected so as to provide an optimum distance between the magnetic head 11 and the measured surface, a magnetic field which is sufficient enough to record data into the vertical magnetic film 4a can stably be secured, even if the vertical distance varies due to a swing of the disk in the vertical direction.
  • FIG. 6 shows a circuit arrangement of the calculating means c 6 used in this instance.
  • the output signals of the light receiving means 5b and 5b' are coupled with a comparator 61 of the calculating means 6, which detects a difference between the output signals.
  • An output signal of the comparator 61 is supplied to a focus lock detect means 62, which may be an operational amplifier.
  • the means 62 constantly monitors the servo signal as represented by the curve (3). When the servo signal is in a servo pull-in range, the focus lock detect means 62 turns on the switch 63, and turns off the switch 64.
  • the output signal of the comparator 61 is also coupled with the moving means 12 by way of the switch 63.
  • a ramp voltage V R is inverted and input to a force drive power source 65, and applied to the moving means 12 by way of the switch 64.
  • the reason why the ramp voltage is inverted is that the direction of the magnetic head servo is opposite to that of the servo for the optical system.
  • the ramp voltage V R is input in a loop open state (in a state where the switch 63 is turned off), and is input through the switch 64 to the moving means 12.
  • the moving means 12 is forcedly moved to a point where it is most distant from the measured surface 4. Then, it is gradually moved toward the measured surface 4.
  • the switch 64 is turned off, and at the same time the switch 63 is turned on to close the loop.
  • the objective lens 23 For the pull-in of the servo for the optical system, the objective lens 23 is gradually moved toward the disk from the point most distant from the disk, with a ramp voltage having the reverse polarity to that of the ramp voltage V R . A zero-cross point of the focus error signal or its neighborhood is detected in a similar manner, and the servo operation is pulled in. It is for this reason that the ramp voltage for the servo pull-in of the optical system is inverted and is used for the servo pull-in of the magnetic head.
  • the switch 63 is turned on, while the switch 64 is turned off.
  • the pull-in point of the servo for the optical system is not always coincident with the optimum servo pull-in point of the magnetic head, but there exists a high probability that the optimum optical servo pull-in point is coincident.
  • an electrical means is used for making a gain of one of the light receiving elements equal to that of the other. This can readily be realized by coupling a variable resistor or a variable gain amplifier with the output of one of the light receiving elements.
  • the magnetic head is heated when it is operated. Due to the generated heat, a temperature of the light receiving elements changes so that dark current is generated which causes the output signals of the light receiving elements possibly to drift. Accordingly, when the gain of one of the light receiving elements is adjusted, its dark current component changes and its balance with that of the other light receiving element is lost. As a result, the off balance appears in the form of an offset component in the differential output signal.
  • the dark current as the DC component can be removed in such a way that light emitted from each light emitting element is modulated, and its amplitude component is picked up by an AC coupling means.
  • the neutral point of the magnetic head 11 is preferably placed at the optimum distance between the head and the disk. However, a slight focus offset will be caused due to the scattering caused by heat. In such a case, a offset voltage is applied to one of the output signals of the photo detectors 5 and 5'. When an apparent error voltage becomes zero, the distance of the magnetic head 11 to the disk has been adjusted to an optimum distance.
  • the output signals of the light receiving means 5b and 5b' are applied to the comparator 61 in the calculating means 6.
  • the comparator 61 produces an output signal representative of a difference between the output signals of the light receiving means 5b and 5b'.
  • the output signal of the compactor 61 is applied through the switch 63 to the moving means 12. Consequently, the magnetic head 11 is moved in the direction of arrow A in FIG. 3, thereby to maintain the distance between the magnetic head 11 and the measured surface at a fixed distance.
  • the measured surface 4 when inclined up from left to right, is denoted as 4'.
  • the measured surface 4 When inclined down from left to right, it is denoted as 4".
  • Upper symbols of (+) and (-) at a bottom portion of FIGS. 7(a) to 9(b) indicate changes of the vertical distance from the light receiving means to the measured surface.
  • Lower symbols of (+) and (-) indicate changes of the positions of the reflected light toward the light receiving means, which are due to an inclination of the disk, in terms of changes of the vertical distance.
  • FIGS. 7(a) and 7(b) show a case where the light emitting means 5a and 5a' and the light receiving means 5b and 5b' are arrayed into a line, and the light emitting means and the light receiving means are alternately arranged.
  • FIG. 7(a) it is assumed that when the measured surface 4 is not slanted, the objective lens is focused. Under this condition, the amount of light incident on the light receiving element 5b is equal to that of light incident on the light receiving element 5b'.
  • the output signal of each light receiving element is at point S in FIG. 5. To be more specific, the output power of the photo detector 5b closer to the measured surface does not yet reach its peak as indicated by the curve (1).
  • the output power of the photo detector 5b' has the profile of (2) in FIG. 5, because, as the reflected light diverges from the measured surface, the reflected light becomes more dispersed from the light emitting means when it is incident on the photo detector 5b', and hence an amount of lost light increases.
  • the reflected light directed toward the light receiving element 5b is deviated in a direction toward the light emitting element 5a as indicated by a dotted line. Accordingly, the amplitude of the output signal of the light receiving element 5b decreases. This is equivalent to such a situation where the photo detector 5 moves nearer to the measured surface, as seen from the curve (1) in FIG. 5.
  • the reflected light from the measured surface 4' changes its path from a solid line path to a dotted line path, and hence, the reflected light is deviated in a direction closer to the light receiving element 5b'. Under this condition, the amount of the reflected light incident on the light receiving element increases. As seen from the curve (2) in FIG. 5, this is equivalent to such a situation where the photo detector 5' moves nearer to the measured surface.
  • both photo detectors produce output powers which are comparable with powers produced by the detectors when the detectors get nearer to the measured surface.
  • the servo system controls the magnetic head 11 so as to become more distant from the measured surface 4.
  • the measured surface is slanted in the direction opposite to that in the case of FIG. 7(a).
  • the incident light to be incident on the light receiving element 5b diverges in a direction away from the light emitting element 5a, as indicated by a dotted line, and accordingly, the power of the light receiving element 5b decreases. This is equivalent to such a situation where the photo detector 5 moves a greater distance away from the measured surface.
  • the photo detector 5' and accordingly, the output power of the light receiving element 5b decreases. This is equivalent to such a situation where the photo detector 5 moves a greater distance away from the measured surface. Under this condition, the servo system operates to move the magnetic head toward the measured surface.
  • an offset component is superposed on the focus error as the result of the inclination of the measured surface 4 resulting in a non-optimal operation.
  • the light emitting means 5a and 5a' are disposed on the inner side of the light receiving means.
  • the divergence of the reflected light incident on the light receiving element 5b resembles that in the case of FIG. 7(a). Accordingly, the output power of the light receiving element 5b decreases. This is equivalent to such a situation where the photo detector 5 moves a close distance toward the measured surface.
  • the reflected light is incident on the light receiving element 5b' at a place more distant from the light emitting element 5a', as in the case where the photo detector 5 moves a greater distance away from the measured surface.
  • the output power of the light receiving element 5b' decreases. Specifically, the output powers of both the light receiving elements 5b and 5b' decrease, and such parallel decrease is canceled out to a certain degree by the comparator 61. Consequently, the adverse effect by the inclination of the measured surface is negligible.
  • the light receiving elements 5b and 5b' are disposed on the inner side of the light emitting elements 5a and 5a', and accordingly, the arrangement of such elements is the reverse of that in FIGS. 8(a) and 8(b).
  • the output powers of the photo detectors 5 and 5' change in the same direction. Accordingly, the change components are canceled out by the comparator 61.
  • a position detector which is little influenced by the inclination of the measured surface can be realized by such an arrangement that the two light emitting means and the two light receiving means are arrayed into a line, and the light emitting means are disposed on the inner side of the light receiving means and vice versa.
  • the position detector of the invention is assembled into the optomagnetic recording/reproducing apparatus, and is operative in order to keep the distance between the magnetic head and the disk constant. It should also be evident to those skilled persons in the art that the position detector of the invention is applicable for any other apparatus of the type in which a distance between two members, relatively disposed, must be kept constant.
  • FIG. 10 is a diagram showing a second embodiment of a position detector according to the present invention.
  • photo detectors 5 and 5' are symmetrically disposed on both sides of a reference measured plane 7, and are fixed to a base 8.
  • Such arrangement can be used to keep a constant distance between the reference measured plane 7 and the measured surface as disposed right above the plane 7, and hence may achieve the objects of the invention more satisfactorily.
  • FIG. 11 is a diagram showing a third embodiment of a position detector according to the present invention.
  • a single light emitting means 5a mounted on the base 8, is used.
  • Two light receiving means 5b and 5b' which are at different vertical levels, are disposed on opposing sides of the light emitting means 5a.
  • the two photo detectors are preferably disposed in the direction orthogonal to the radius of the optical disk. Otherwise, as the magnetic head 11 moves along the measured surface 4 radius of the disk, the light emitting means or the light receiving means of the photo detectors move beyond the circumferential limits of the disk. In this case, operation is degraded as the light goes outside the disk or the light receiving means cannot receiving the light.
  • the light emitting means and the light receiving means may be closely disposed, realizing a size reduction of the position detector.
  • the two light emitting means and the two light receiving means are arrayed into a line, and the light emitting elements are disposed on the inner side of the light receiving means and vice versa, the adverse influence by the inclination of the measured surface can be substantially reduced, thus providing a more exact position measurement.
  • a fourth embodiment of the present invention will be described with reference to FIG. 12.
  • a position detector according to the present invention is incorporated into an optomagnetic recording/reproducing apparatus.
  • like reference numerals are used for designating like or equivalent portions in FIG. 3. Description will be given placing an emphasis on only those portions of the fourth embodiment that are different from the first embodiment of FIG. 3.
  • the magnetic head 11 is provided with a support table 11' that is integral therewith.
  • the magnetic head 11 is aligned with the light emitting means 9a in the radial direction of the disk.
  • the light receiving means 9b and 9c are each rectangular in shape as viewed from above and separated from the light emitting means 9a by different distances.
  • a circle 9d indicates an illumination area including the light receiving elements 9b and 9c, i.e., the light beam, which is emitted from the light emitting means 9a and reflected from the measured surface 4, falls within the area of the circle 9d.
  • the radius of the circle 9d becomes large in proportion with an increased distance H between the light emitting means 9a and the measured surface 4 (see FIG. 12).
  • the light emitted from the light emitting means 9a is reflected by the area 9d on the measured surface 4 and is incident on the light receiving means 9b and 9c.
  • Each of the light receiving means 9b and 9c produces an output signal which depends on an intensity of the reflected light, and applies it to the calculating means 6. Then, the calculating means 6 supplies a drive current to the moving means 12.
  • the drive current becomes zero when the distance between the magnetic head 11 and a vertical magnetic film 4a of the disk 4 reaches the optimum value.
  • the polarity and level of the drive current changes and varies in accordance with a displacement of the head in the vertical direction. This will subsequently be described in detail.
  • the light emitting means 9a of the photo detector 9 irradiates the measured surface 4 within the circular area 9d whose radius depends on the distance H from the disk 4 (FIG. 13). Part of the reflected light from the disk 4 is incident on, and detected by, the light receiving means 9b and 9c, which in turn produce output signals reflecting the amounts of the received light.
  • a graphical representation of a relationship between an output signal P of each light receiving means 9b and 9c and the distance H between the disk 4 and the photo detector is as shown in FIG. 14.
  • the ordinate represents the output power P of the light receiving means
  • the abscissa represents the distance H.
  • a curve (2) indicates a variation of the output power P of the light receiving means 9c which is more distant from the light emitting means 9a.
  • a profile of the curve (2) resembles that of the curve (1), but is shifted to the right as a whole, since the distance of the light receiving means is more distant from the light submitting means 9a.
  • a light receiving area of the light receiving means 9c is larger than that of the light receiving means 9b, in order that an amount of the reflected light received by the light receiving means 9c is substantially equal to that received by the light receiving means 9b (and, accordingly, a peak level of the curve (1) is substantially equal to that of the curve (2)).
  • a difference between the curves (1) and (2) provides an S-shaped curve (3).
  • the magnetic head 11 is moved, thereby to maintain a fixed distance between the magnetic head 11 and the measured surface 4.
  • a position of the magnetic head 11 relative to the photo detector 9 is selected so as to provide an optimum distance between the magnetic head 11 and the measured surface, a magnetic field sufficient enough to record data into the vertical magnetic film 4a can always be secured even if the vertical distance varies due to a swing of the disk in the vertical direction.
  • a circuit arrangement as shown in FIG. 6 is used as the arithmetic calculating means 6.
  • the output signal of the light receiving means 9b is applied to the noninverting input terminal of the comparator 61, while the output signal of the light receiving means 9c, is applied to the inverting input terminal.
  • the comparator 61 In a normal servo state, the comparator 61 produces an output signal representative of a difference between the output powers of the light receiving means 9b and 9c.
  • the output signal of the comparator 61 is applied through the switch 63 to the moving means 12. Consequently, the magnetic head 11 is moved in the direction of arrow A in FIG. 12, thereby to maintain the distance between the magnetic head 11 and the measured surface 4 at a fixed distance.
  • the drive signal is directly applied to the moving means 12 from the focus servo unit 31.
  • a measure must be taken for a deviation of the frequency characteristic that is caused by a weight imbalance of the optical head against the magnetic head, and a displacement of the neutral position due to fatigue of the plate spring 13, and the like.
  • the focus servo system for the optical system is different from the control system to maintain the distance between the magnetic head and the disk at a fixed value. Because of this feature, the position detector of the present invention is free from the displacement of the neutral point due to spring fatigue and the deviation of the frequency characteristic due to weight imbalance.
  • FIG. 15 is a diagram showing a fifth embodiment of a position detector according to the present invention.
  • the light receiving means 9b and 9c occupies the upper and lower portion of an equilateral triangle respectively.
  • the triangle is disposed so that its vertex is closer to the light emitting means 9a.
  • the light receiving means 9b and 9c are different in size with respect to light receiving areas and their distances to the light emitting means 9a as viewed in the horizontal direction. Accordingly, such position detector is operable like the embodiment of FIG. 14, and hence, can produce a servo signal to maintain the distance between the photo detector 9 and the measured surface 4 at a fixed value.
  • FIG. 16 is a diagram showing a sixth embodiment of a position detector according to the present invention.
  • the light receiving means 9b and 9c when coupled, form a trapezoid with a top side closer to the light emitting means 9a.
  • the bottom side of the triangular light receiving means 9b and the vertex of the triangular light receiving means 9c are both disposed closer to the light emitting means 9a.
  • the centriod of the light receiving area of the light receiving means 9b is closer to the light emitting means 9a than that of the light receiving means 9c.
  • the output power of the light receiving means 9b varies as indicated by a curve (1) in FIG. 17. As shown, it steeply rises to reach a peak, and gradually falls off.
  • the output power of the light receiving means 9b as indicated by a curve (2), gently rises to reach a peak, and steeply falls off.
  • a difference of the curves (1) and (2) provides an S-shaped curve (3), that resembles the curve (3) in FIG. 14.
  • FIG. 18 is a diagram showing a seventh embodiment of a position detector according to the present invention.
  • the position detector of the instant embodiment is capable of correcting both the vertical distance from the measured surface and the inclination of the measured surface.
  • a pair of opposing light receiving means 9b and 9c, and 9b', arranged as shown in FIG. 16, are symmetrically disposed with respect to the light emitting means 9a.
  • a calculating means 7 is provided.
  • the sum of the output signals of the light receiving means 9b and 9b' is calculated by an adder 71.
  • the sum of the output signals of the light receiving means 9c and 9c' is calculated by an adder 72.
  • the output signals of the adders 71 and 82 are compared by a comparator 73, thereby to calculate a quantity usable for correcting the vertical distance H.
  • the correction quantity is then applied to the moving means 12.
  • the sum of the output signals of the light receiving means 9b and 9c is calculated by the adder 74.
  • the sum of the output signals of the light receiving means 9b' and 9c' are calculated by the adder 75.
  • the output signals of the adders 74 and 75 are compared by a comparator 76, and the result of the comparison is applied to inclination correcting means 17.
  • the inclination correcting means is able to correct an inclination of the measured surface in a known manner.
  • a signal ⁇ P indicates part of the output signal of the comparator 73 which is applied to the comparator 76, for the inclination detection. An inclination error due to height is corrected by using this quantity ⁇ P.
  • the distance correction can be made through the comparison of the output signals from the light receiving means which are located at different distances from the light emitting means 9a, i.e., the result of comparing the output signals of the light receiving means 9b and 9c or 9b' and 9c'.
  • the inclination correction can be made through the comparison of the output signals from the light receiving means which are symmetrically disposed with respect to the light emitting means 9a, i.e., the result of comparing the output signals of the light receiving means 9b and 9b' or 9c and 9c'.
  • the two light receiving means are preferably disposed in the direction orthogonal to the radius of the optical disk. Otherwise, as the magnetic head 11 moves along the radius of the disk, the light emitting means or the light receiving means of the photo detectors move beyond the circumferential boundary of the disk. In this case, the light goes outside the disk or the light receiving means cannot receive the light.
  • the light emitting means and the light receiving means may be closely disposed, realizing a size reduction of the position detector.
  • the two light emitting means and the two light receiving means are arrayed into a line, and the light emitting elements are disposed on the inner side of the light receiving means and vice versa, the adverse influence of an inclination of the measured surface can be remarkably reduced, thus providing a more exact position measurement.
  • the light emitting means and the light receiving means are closely disposed. Therefore, the resultant position detector is simple in construction and small in size.
  • the distance between the light emitting means and the measured surface can be controlled to be constant, and the inclination angle of the measured surface can be corrected.

Landscapes

  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Length Measuring Devices By Optical Means (AREA)
US07/608,926 1990-02-08 1990-11-05 Position detector for maintaining a fixed distance between two objects Expired - Lifetime US5162661A (en)

Applications Claiming Priority (4)

Application Number Priority Date Filing Date Title
JP2027189A JPH0782653B2 (ja) 1990-02-08 1990-02-08 位置検出器
JP2-27190 1990-02-08
JP2027190A JPH0782654B2 (ja) 1990-02-08 1990-02-08 位置検出器
JP2-27189 1990-02-08

Publications (1)

Publication Number Publication Date
US5162661A true US5162661A (en) 1992-11-10

Family

ID=26365087

Family Applications (1)

Application Number Title Priority Date Filing Date
US07/608,926 Expired - Lifetime US5162661A (en) 1990-02-08 1990-11-05 Position detector for maintaining a fixed distance between two objects

Country Status (3)

Country Link
US (1) US5162661A (fr)
EP (3) EP0599806B1 (fr)
DE (3) DE69016639T2 (fr)

Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5276631A (en) * 1990-03-28 1994-01-04 Landis & Gyr Betriebs Ag Process for automatic calibration or re-calibration of measurements of a physical variable
US5291268A (en) * 1991-04-27 1994-03-01 Deutsche Forschungsanstalt Fur Luft- Und Raumfahrt Method and apparatus for determining a path difference in a Michelson interferometer
US5327082A (en) * 1992-01-13 1994-07-05 Valmet Automation (Canada) Ltd. On line electromagnetic web thickness measuring apparatus incorporating a servomechanism with optical distance measuring
US5369462A (en) * 1992-06-09 1994-11-29 Olympus Optical Co., Ltd. Inclination detecting apparatus and camera for detecting hand shake using the same
US5448535A (en) * 1990-09-25 1995-09-05 Sony Corporation Head position control device
US5745450A (en) * 1993-04-02 1998-04-28 Sony Corporation Focusing servo system and focus servo acquisition enable with multiple velocity acquisition modes
US6888694B2 (en) * 2002-01-15 2005-05-03 Agency For Science, Technology And Research Active control system and method for reducing disk fluttering induced track misregistrations
EP1548398A1 (fr) * 2003-12-22 2005-06-29 Voith Paper Patent GmbH Dispositif pour la mesure de l'épaisseur d'une bande en mouvement
US20220137321A1 (en) * 2020-01-20 2022-05-05 Lecc Technology Co., Ltd. Laser module

Families Citing this family (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH05334703A (ja) * 1992-05-29 1993-12-17 Matsushita Electric Ind Co Ltd ミラー移動量検出装置
JPH11273116A (ja) * 1998-03-20 1999-10-08 Fujitsu Ltd 光学的情報記憶装置
JP2000283709A (ja) 1999-03-29 2000-10-13 Ando Electric Co Ltd 移動体の位置検出装置と光干渉計
US20060072387A1 (en) * 2002-05-30 2006-04-06 Koninklijke Philips Electroncis N.V. Small optical disk drive
DE102016200505A1 (de) * 2016-01-16 2017-07-20 Robert Bosch Gmbh Mikrospiegelvorrichtung

Citations (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE2155049A1 (de) * 1970-11-06 1972-05-10 Compteurs Comp D Optische Vergleichsvorrichtung mit optischen Fasern
FR2399000A1 (fr) * 1977-07-27 1979-02-23 Sagem Capteur de proximite a guides dielectriques d'ondes optiques
US4358960A (en) * 1979-05-04 1982-11-16 Ladd Research Industries, Inc. Differential fiber optic proximity sensor
US4412746A (en) * 1980-07-16 1983-11-01 The President of Muroran Institute for Technology Optical noncontacting detector
US4488813A (en) * 1982-04-29 1984-12-18 Mechanical Technology Incorporated Reflectivity compensating system for fiber optic sensor employing dual probes at a fixed gap differential
US4670659A (en) * 1979-11-26 1987-06-02 European Electronic Systems Limited Calibration method for an optical measuring system employing reference grids in a series of reference planes
US4711577A (en) * 1985-03-08 1987-12-08 Mechanical Technology Incorporated Optical configuration of fiber optic sensor for symmetric dynamic response about the optical null
US4798964A (en) * 1985-08-12 1989-01-17 Wilhelm Hegenscheidt Gesellschaft Mbh Method and apparatus for the contactless measuring of the tread quality of railroad
US4807212A (en) * 1986-03-24 1989-02-21 Hitachi, Ltd. Correcting for comatic aberration in an optical head of an optical disk apparatus
US4899061A (en) * 1986-08-13 1990-02-06 The Broken Hill Proprietary Company Limited Determining a width and/or thickness of a generally rectangular object

Patent Citations (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE2155049A1 (de) * 1970-11-06 1972-05-10 Compteurs Comp D Optische Vergleichsvorrichtung mit optischen Fasern
FR2399000A1 (fr) * 1977-07-27 1979-02-23 Sagem Capteur de proximite a guides dielectriques d'ondes optiques
US4358960A (en) * 1979-05-04 1982-11-16 Ladd Research Industries, Inc. Differential fiber optic proximity sensor
US4670659A (en) * 1979-11-26 1987-06-02 European Electronic Systems Limited Calibration method for an optical measuring system employing reference grids in a series of reference planes
US4412746A (en) * 1980-07-16 1983-11-01 The President of Muroran Institute for Technology Optical noncontacting detector
US4488813A (en) * 1982-04-29 1984-12-18 Mechanical Technology Incorporated Reflectivity compensating system for fiber optic sensor employing dual probes at a fixed gap differential
US4711577A (en) * 1985-03-08 1987-12-08 Mechanical Technology Incorporated Optical configuration of fiber optic sensor for symmetric dynamic response about the optical null
US4798964A (en) * 1985-08-12 1989-01-17 Wilhelm Hegenscheidt Gesellschaft Mbh Method and apparatus for the contactless measuring of the tread quality of railroad
US4807212A (en) * 1986-03-24 1989-02-21 Hitachi, Ltd. Correcting for comatic aberration in an optical head of an optical disk apparatus
US4899061A (en) * 1986-08-13 1990-02-06 The Broken Hill Proprietary Company Limited Determining a width and/or thickness of a generally rectangular object

Cited By (13)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5276631A (en) * 1990-03-28 1994-01-04 Landis & Gyr Betriebs Ag Process for automatic calibration or re-calibration of measurements of a physical variable
US5448535A (en) * 1990-09-25 1995-09-05 Sony Corporation Head position control device
US5291268A (en) * 1991-04-27 1994-03-01 Deutsche Forschungsanstalt Fur Luft- Und Raumfahrt Method and apparatus for determining a path difference in a Michelson interferometer
US5327082A (en) * 1992-01-13 1994-07-05 Valmet Automation (Canada) Ltd. On line electromagnetic web thickness measuring apparatus incorporating a servomechanism with optical distance measuring
US5369462A (en) * 1992-06-09 1994-11-29 Olympus Optical Co., Ltd. Inclination detecting apparatus and camera for detecting hand shake using the same
US5912867A (en) * 1993-04-02 1999-06-15 Sony Corporation Focusing servo system with focus servo acquisition enable which is operational within a predetermined time after the start of the movement of an objective lens
US5745450A (en) * 1993-04-02 1998-04-28 Sony Corporation Focusing servo system and focus servo acquisition enable with multiple velocity acquisition modes
US6888694B2 (en) * 2002-01-15 2005-05-03 Agency For Science, Technology And Research Active control system and method for reducing disk fluttering induced track misregistrations
EP1548398A1 (fr) * 2003-12-22 2005-06-29 Voith Paper Patent GmbH Dispositif pour la mesure de l'épaisseur d'une bande en mouvement
US20050157314A1 (en) * 2003-12-22 2005-07-21 Pekka Typpoe Measuring device
US7319521B2 (en) 2003-12-22 2008-01-15 Voith Paper Patent Gmbh Measuring device
US20220137321A1 (en) * 2020-01-20 2022-05-05 Lecc Technology Co., Ltd. Laser module
US11921344B2 (en) * 2020-01-20 2024-03-05 Lecc Technology Co., Ltd. Laser module

Also Published As

Publication number Publication date
EP0447713A3 (en) 1991-10-23
DE69016639D1 (de) 1995-03-16
EP0447713B1 (fr) 1995-02-01
EP0599806B1 (fr) 1996-08-28
DE69016639T2 (de) 1995-10-05
DE69028322T2 (de) 1997-03-20
EP0599806A1 (fr) 1994-06-01
EP0447713A2 (fr) 1991-09-25
EP0599807B1 (fr) 1996-06-12
DE69027454D1 (de) 1996-07-18
DE69028322D1 (de) 1996-10-02
DE69027454T2 (de) 1997-01-23
EP0599807A1 (fr) 1994-06-01

Similar Documents

Publication Publication Date Title
US5162661A (en) Position detector for maintaining a fixed distance between two objects
US4006293A (en) Apparatus for reading a flat record carrier with an optically readable information structure
US5247493A (en) Magneto-optical recording and reproducing disk device having a bimorph type actuator with specific structures for mounting a magnetic head in opposing to the surface of the disk
EP0044074A1 (fr) Détecteur de foyer
US5305294A (en) Magneto-optical recording/reproducing system having an electromagnetic actuator
JPH02281431A (ja) 対物レンズ駆動装置
US4899327A (en) Focus servo loop correction
JPH0656286B2 (ja) 位置検出装置
US4888752A (en) Focusing and tracking servo system for controlling the projection of an optical beam on an optical disk
EP0089244B1 (fr) Appareil de commande de la position d'un faisceau lumineux
US5293366A (en) Information recording and reproducing apparatus provided with means for adding to a tracking signal offset corresponding to the positional deviation of a recording spot and a reproducing spot
EP0661697A1 (fr) Technique d'asservissement d'un système d'enregistrement et de lecture optique
US6521878B2 (en) Radial tilt detector for an optical disc
US4926407A (en) Optical data processor
JPH056564A (ja) 光デイスク読取り装置におけるトラツキング誤差検出方式
EP0190439A2 (fr) Correction de la boucle d'asservissement de focalisation
JPH0782654B2 (ja) 位置検出器
EP0367465B1 (fr) Dispositifs d'enregistrement optique
JPH0782653B2 (ja) 位置検出器
KR19990050071A (ko) 포커스 바이어스 조정 장치
JP2887273B2 (ja) 光学式ピックアップ装置
JPS6366736A (ja) デイスク傾斜度検出装置
JPH04219655A (ja) ヘツド位置制御装置
JPH0792941B2 (ja) 磁界コイル位置制御装置
JPH04113527A (ja) 光ピックアップ装置

Legal Events

Date Code Title Description
AS Assignment

Owner name: PIONEER ELECTRONIC CORPORATION, JAPAN

Free format text: ASSIGNMENT OF ASSIGNORS INTEREST.;ASSIGNORS:SATO, KATSUHARU;TANIGUCHI, SHOJI;YANAGAWA, NAOHARU;REEL/FRAME:005507/0020

Effective date: 19901029

STCF Information on status: patent grant

Free format text: PATENTED CASE

FPAY Fee payment

Year of fee payment: 4

FPAY Fee payment

Year of fee payment: 8

FEPP Fee payment procedure

Free format text: PAYOR NUMBER ASSIGNED (ORIGINAL EVENT CODE: ASPN); ENTITY STATUS OF PATENT OWNER: LARGE ENTITY

FPAY Fee payment

Year of fee payment: 12